The state prison guards union, responding to weeks of accusations that some of its members engaged in abuse of prisoners and misconduct, has launched a $30,000 radio advertising campaign intended to gain public support.

The campaign begins about a month after the killing of defrocked priest John J. Geoghan, allegedly by another inmate, at the maximum-security Souza-Baranowski Correctional Center in Shirley.

In the ad, a male voice speaks from the point of view of one of the state's 5,000 guards.

''You will be cursed at, spit at. Have human waste thrown at you,'' the voice says. ''You will see killers trying to kill again. There may by be a riot. You could be taken hostage, assaulted, beaten.

''You will search for hidden knives. Meet inmates with AIDS who want to give you the disease that will kill them. At any moment you could be killed. That's what's it feels like to be a Massachusetts correction officer.''

Since Geoghan's death Aug. 23, news reports have quoted from numerous written accounts depicting guards as abusing Geoghan, including one authored by Geoghan in 2002, while he was in the protective custody unit of the medium-security Concord state prison.

That alleged abuse contributed to the decision to transfer Geoghan to the maximum-security Souza-Baranowski Correctional Center.

When he was killed, Geoghan was serving a nine- to 10-year sentence for molesting a 10-year-old boy.